A local area network (LAN) is characterized by its high data transmission rate, and the fact that, in general, the communication channel of the network is shared by all the workstations and devices connected to that particular network. There are a variety of techniques for enabling devices connected to a network to communicate with each other. One such technique is the use of a token ring, whereby a "token" is continuously circulated among the connected devices; messages and data to be transmitted from one device to another are appended to the token. The performance of a token ring is measured by the speed at which data is transmitted on the ring; standard token ring data rates are 4 Mbps (megabits per second) and 16 Mbps.
Users of token ring systems face the problem of how to increase performance without replacing their existing systems. The present invention describes a solution to that problem: namely, by adding a plurality of independent token rings or channels, operating in parallel and at the same data rate as the existing ring, in order to increase the capacity, or bandwidth, of the system. The technique described in this invention can be implemented without changing existing interfaces or protocols, and conforms with IEEE communications standards.
Among the related prior art to local area network systems, U.S. Pat. No. 4,766,590 describes a scheme for connecting a plurality of stations to form a single serial transmission loop, so as to vary the order of connections of the stations of the loop. The patent fails to address the subject of multiple backbone channels or techniques to utilize the capacity of multiple channels; the use of multiple channels is an integral part of the present invention.
The subject matter of U.S. Pat. No. 4,468,733 is a scheme for building a serial bus loop system consisting of multiple serial bus loops, in order to increase the reliability of a single bus loop system. The patent involves a flat network with one channel of communication for multiple devices, unlike the present invention which utilizes multiple channels of communication for multiple devices.
A third related patent is U.S. Pat. No. 3,748,647, which describes a scheme for interconnecting a plurality of shift registers into a plurality of rings, each ring consisting only of shift registers and logic related to controlling shift registers. The patent addresses only information contained in fixed length registers, not in variable length frames which are used by local area networks. The patent significantly differs from the present invention in that it fails to address local area networks, conformance to network standards, or the optimal and reliable use of available bandwidth.